Microfluidic Fabrication of Nanoparticles Based on Ethyl Acrylate-Functionalized Chitosan for Adsorption of Methylene Blue from Aqueous Solutions

The adsorption of nanoparticle (NP)-based adsorbents especially those made of polymers to remove dyes as toxic substances from pollutants is yet remained as a critical issue. The objective of this work was to prepare microfluidic (MF) fabrication of NPs based on ethyl acrylate (EA)-functionalized chitosan (CS) for methylene blue (MB) dye removal from aqueous solutions. For this purpose, a series of experiments such as FTIR, SEM alongside DLS, and UV-vis spectrophotometry were carried out to investigate the physicochemical properties of the samples. The FTIR spectra showed that the amine (-NH2) and hydroxyl (-OH) groups on CS structure were replaced with EA, appropriately. The SEM and DLS results depicted that EA-functionalized CS NPs fabricated using MF technique had uniform shapes, and the diameters as small as 70nm compared to those samples produced via bulk mixing (BM) method (similar to 300nm). Moreover, the surface charge of MF-assisted CS NPs after functionalization exhibited the lower zeta potential value (similar to+11) than that of samples based on BM (similar to+14) due to occurring the laminar flow through the micro-channels embedded in the MF chip, leading to an increase in the MB adsorption. Subsequently, at the optimized amounts of the dye concentration (89.12mgL(-1)), the adsorbent concentration (1.38gL(-1)), and pH (10.58) by means of Box-Behnken design (BBD) method, the maximum percentage of MB removal by the use of MF-fabricated EA-functionalized CS NPs was 98.4%. By fitting the obtained adsorption data to the isotherm models such as Lagmuir, Freundlich, and Temkin, it has been found that the adsorption mechanism followed the Langmuir model (maximum capacity of the adsorption 384.61mg/g), which assumed a monolayer coverage of MB molecules as adsorbates over a homogeneous adsorbent surface.